Semiconductor device and method of manufacturing a semiconductor device

ABSTRACT

A semiconductor device includes: a substrate; a wiring formed above the substrate; a titanium nitride film formed on the wiring; an oxide film formed on the titanium nitride film; a silicon nitride film formed on the oxide film; and a pad portion exposing the wiring, and formed at a place where a first opening portion formed in the silicon nitride film and a second opening portion formed in the titanium nitride film overlap with each other in plan view, and being inside a third opening portion formed in the oxide film in plan view, wherein the silicon nitride film is formed on top of and in contact with the titanium nitride film inside the third opening portion in plan view.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to JapanesePatent Application No. 2017-048799 filed on Mar. 14, 2017, the entirecontent of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a semiconductor device and a method ofmanufacturing a semiconductor device.

2. Description of the Related Art

An existing semiconductor device includes a wiring made of aluminum oran aluminum alloy and formed on a substrate, an anti-reflection filmmade of titanium nitride and formed on the wiring, and an oxide filmformed on the anti-reflection film, and a pad portion which exposes thewiring is formed at a place where an opening portion formed in the oxidefilm and an opening portion formed in the anti-reflection film overlapwith each other in plan view.

In a semiconductor device having such a structure, titanium nitrideforming the anti-reflection film is sometimes corroded in a portionsurrounding the opening portion by a long-term reliability test thatinvolves bias application under a high-temperature and high-humidityenvironment, abbreviated as THB (Temperature Humidity Bias).

To solve this problem, a semiconductor device has been proposed in whichtitanium nitride forming the anti-reflection film is not exposed in theopening portion.

For example, in Japanese Patent No. 5443827, there is proposed asemiconductor device including: a first surface protection film with afirst opening portion formed above a pad; and a second surfaceprotection film formed on the pad and the first surface protection filmto have a second opening portion above the pad, in which the padincludes a first conductor film and an anti-reflection film formed onthe first conductor film, the second opening portion is contained in aninner region of the first opening portion, and the anti-reflection filmis removed from the inner region of the first opening portion.

However, the technology described in Japanese Patent No. 5443827 whichinvolves removing the anti-reflection film from the inner region of thefirst opening portion formed in the first surface protection film has aproblem in that, after the first surface protection film formed from asilicon oxide film is patterned and etched in order to form the firstopening portion, etching gas needs to be switched to etch and remove theanti-reflection film made of titanium nitride, thereby increasing thenumber of steps.

In addition, in a semiconductor device of the related art, particularlyone in which a silicon oxide film is formed on an anti-reflection filmmade of titanium nitride, the anti-reflection film may change intotitanium oxide due to the long-term reliability test (THB) that involvesbias application under a high-temperature and high-humidity environment,resulting in a possible impairment of the external appearance.

SUMMARY OF THE INVENTION

The present invention provides a semiconductor device that is resistantto the corrosion of titanium nitride forming an anti-reflection film,despite the placement of a silicon oxide film on the anti-reflectionfilm made of titanium nitride, and is reduced in the number ofmanufacturing steps, and a method of manufacturing the semiconductordevice.

Through extensive research, the inventors of the present invention havethought of a semiconductor device in which a pad portion exposing awiring is formed at a place where a first opening portion formed in asilicon nitride film, which serves as a protection film, and a secondopening portion formed in a titanium nitride film, which serves as ananti-reflection film, overlap with each other in plan view, and isinside a third opening portion formed in an oxide film in plan view, andthe silicon nitride film is formed on top of and in contact with thetitanium nitride film inside the third opening portion in plan view,which leads to the present invention.

Specifically, the present invention relates to the following items.

According to one embodiment of the present invention there is provided asemiconductor device including:

a substrate;

a wiring formed above the substrate;

a titanium nitride film formed on the wiring;

an oxide film formed on the titanium nitride film;

a silicon nitride film formed on the oxide film; and

a pad portion exposing the wiring, and formed at a place where a firstopening portion formed in the silicon nitride film and a second openingportion formed in the titanium nitride film overlap with each other inplan view, and being inside a third opening portion formed in the oxidefilm in plan view, and

the silicon nitride film being formed on top of and in contact with thetitanium nitride film inside the third opening portion in plan view.

According to one embodiment of the present invention there is provided amethod of manufacturing a semiconductor device including:

forming a wiring above a substrate;

forming a titanium nitride film on the wiring;

forming an oxide film on the titanium nitride film, and patterning theoxide film to form a third opening portion which exposes the titaniumnitride film at a bottom of the third opening portion through the oxidefilm;

forming a silicon nitride film on the oxide film and on the thirdopening portion; and

etching the silicon nitride film and the titanium nitride filmsuccessively with the same etching gas to form a pad portion whichpenetrates the silicon nitride film and the titanium nitride film, andwhich exposes the wiring at the bottom inside the third opening portionin plan view.

In the semiconductor device of the present invention, the pad portionexposing the wiring is formed at a place where the first opening portionformed in the silicon nitride film and the second opening portion formedin the titanium nitride film overlap with each other in plan view, andis inside the third opening portion formed in the oxide film in planview, and the silicon nitride film is formed on top of and in contactwith the titanium nitride film inside the third opening portion in planview. This makes the titanium nitride film serving as theanti-reflection film resistant to corrosion, thereby giving thesemiconductor device high reliability.

Further, in the semiconductor device of the present invention, the padportion exposing the wiring is formed at a place where the first openingportion formed in the silicon nitride film and the second openingportion formed in the titanium nitride film overlap with each other inplan view, and is inside the third opening portion formed in the oxidefilm in plan view, and the silicon nitride film is formed on top of andin contact with the titanium nitride film inside the third openingportion in plan view. The first opening portion and the second openingportion can thus be formed by etching the silicon nitride film and thetitanium nitride film successively with the use of the same mask and thesame etching gas, contributing efficient production of the semiconductordevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view for illustrating an example of asemiconductor device according to the present invention.

FIG. 2 is a plan view for illustrating planar arrangement around a padportion in the semiconductor device of FIG. 1.

FIG. 3 is a process view for illustrating an example of a method ofmanufacturing the semiconductor device of FIG. 1 and FIG. 2.

FIG. 4 is a process view for illustrating the example of the method ofmanufacturing the semiconductor device of FIG. 1 and FIG. 2.

FIG. 5 is a process view for illustrating the example of the method ofmanufacturing the semiconductor device of FIG. 1 and FIG. 2.

FIG. 6 is a process view for illustrating the example of the method ofmanufacturing the semiconductor device of FIG. 1 and FIG. 2.

FIG. 7 is a plan view for illustrating planar arrangement around the padportion in the step of FIG. 6.

FIG. 8 is a process view for illustrating the example of the method ofmanufacturing the semiconductor device of FIG. 1 and FIG. 2.

FIG. 9 is a schematic sectional view for illustrating an example of asemiconductor device of the related art.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The inventors of the present invention have acquired the followingfindings as a result of extensive research.

The inventors of the present invention have examined the corrosion ofthe titanium nitride film caused by a long-term reliability test (THB)that involves bias application under a high-temperature andhigh-humidity environment in a semiconductor device of the related artwhich includes an anti-reflection film made of titanium nitride.

The examination has revealed that a surface of the titanium nitride filmwhich opposes the oxide film in the vicinity of the opening portion forexposing the pad portion is particularly liable to corrode when thetitanium nitride film and an oxide film are formed on a wiring in thestated order, and a pad portion which exposes the wiring is formed at aplace where a third opening portion formed in the oxide film and asecond opening portion formed in the titanium nitride film overlap witheach other in plan view.

It is presumed that the corrosion in the surface of the titanium nitridefilm which opposes the oxide film is accelerated by the generation oftitanium oxide as a result of reaction between titanium atoms in thetitanium nitride film and moisture infiltrating through the oxide filmfrom the opening portion for exposing the pad portion because thegeneration of titanium oxide lowers the adhesion of the opposingsurface, thereby allowing more moisture to infiltrate in the opposingsurface.

In view of this, the inventors of the present invention have made afurther study on the titanium nitride film as an anti-reflection film,the oxide film formed on the titanium nitride film, and the siliconnitride film formed as a protection film on the oxide film, while payingattention to planar arrangement around the pad portion. A positionalrelation effective against the corrosion has been found as a result, inwhich the pad portion is formed inside the third opening portion formedin the oxide film in plan view, and the silicon nitride film is formedon top of and in contact with the titanium nitride film inside the thirdopening portion in plan view. In this positional relation, the firstopening portion formed in the silicon nitride film and the secondopening portion formed in the titanium nitride film have the same sizeand are positioned in overlapping places, thereby defining the perimeterof the pad portion, and the oxide film is placed apart from the padportion. It may therefore be said that the third opening portion formedin the oxide film is outside the first opening portion and the secondopening portion.

In a semiconductor device having this positional relation, the absenceof the oxide film inside the third opening portion in plan view meansthat the titanium nitride film does not have the surface which opposesthe oxide film and which is susceptible to corrosion, inside the thirdopening portion in plan view. In addition, the silicon nitride film,which has fine water resistance, is formed on top of and in contact withthe titanium nitride film inside the third opening portion in plan view.Moisture can consequently be prevented from infiltrating in the surfaceof the titanium nitride film which opposes the oxide film from theopening portion for exposing the pad portion. The contact between thesilicon nitride film and the top of the titanium nitride film alsosupplies nitrogen atoms from the silicon nitride film to the titaniumnitride film, which causes reaction between dangling bonds of titaniumatoms in the titanium nitride film and nitrogen atoms in the siliconnitride film. A dangling bond in a titanium atom tends to react withmoisture infiltrating from the opening portion for exposing the pad,resulting in the generation of titanium oxide. In contrast, when adangling bond in a titanium atom is occupied with a nitrogen atom asdescribed above, moisture entering the titanium nitride film has a smallchance of causing the generation of titanium oxide. As a result,corrosion is hardly caused on the titanium nitride film, and hencedetachment at the boundary between the titanium nitride film and thesilicon nitride film can be prevented, and the semiconductor device canbe given high reliability.

The inventors of the present invention have also found out that, whenthe pad portion which exposes the wiring is formed at a place where thefirst opening portion formed in the silicon nitride film and the secondopening portion formed in the titanium nitride film overlap with eachother in plan view, and is inside the third opening portion formed inthe oxide film in plan view, and the silicon nitride film is formed ontop of and in contact with the titanium nitride film inside the thirdopening portion in plan view, production of the semiconductor device isefficient for a reason given below.

In the semiconductor device structured as this, the first openingportion to be formed in the silicon nitride film and the second openingportion to be formed in the titanium nitride film are formedcontinuously on an inner wall of the opening for exposing the padportion. The first opening portion and the second opening portion canaccordingly be formed by etching the silicon nitride film and thetitanium nitride film successively with the use of the same mask. Inaddition, the same etching gas can be used to etch the silicon nitridefilm and the titanium nitride film. Efficient production of thesemiconductor device is therefore accomplished by the successive etchingmethod which uses the same etching gas and does not require switchingthe etching gas when the titanium nitride film is to be etched after theetching of the silicon nitride film.

The present invention is described in detail below with reference to thedrawings. Some of the drawings referred to in the following descriptionare enlarged views of characteristic portions, which are enlarged forconvenience of making the characteristics of the present inventionunderstood easier, and the ratios of the dimensions of components to oneanother and the like may differ from actuality. The materials,dimensions, and the like given in the following description are anexample, and the present invention is not limited thereto. The presentinvention can be carried out in suitably varied modes without losing theeffects of the present invention.

[Semiconductor Device]

FIG. 1 is a schematic sectional view for illustrating an example of asemiconductor device according to the present invention. FIG. 2 is aplan view for illustrating planar arrangement around a pad portion inthe semiconductor device of FIG. 1. The horizontal direction in FIG. 2corresponds to the horizontal direction in FIG. 1.

A semiconductor device 10 of this embodiment includes a substrate 1, awiring 6 which is formed above the substrate 1 with an interlayerinsulating film 2 interposed between the two, a titanium nitride film 7which is formed on the wiring 6 to serve as an anti-reflection film, anoxide film 3 which is formed on the titanium nitride film 7, and asilicon nitride film 4 which is formed on the oxide film 3 to serve as aprotection film.

As illustrated in FIG. 1 and FIG. 2, in the semiconductor device 10according to this embodiment, a pad portion 8 exposing the wiring 6 isformed at a place where a first opening portion 91 formed in the siliconnitride film 4 and a second opening portion 92 formed in the titaniumnitride film 7 overlap with each other in plan view.

The pad portion 8 in the semiconductor device 10 according to thisembodiment is also positioned, in plan view, inside a third openingportion 93 formed in the oxide film 3 as illustrated in FIG. 2.

The silicon nitride film 4 in the semiconductor device 10 according tothis embodiment is formed on top of and in contact with the titaniumnitride film 71 inside the third opening portion 93 in plan view asillustrated in FIG. 1 and FIG. 2.

A substrate made of silicon or other known materials can be used as thesubstrate 1.

The interlayer insulating film 2 can be a known insulating film, forexample, a SiO₂ film, or an oxide film having tetraethyl orthosilicate(TEOS) (Si(OC₂H₅)₄) as a raw material.

The oxide film 3 is a protection film, and is formed so as to cover thewiring 6 which has on a top surface thereof the titanium nitride film 7serving as an anti-reflection film.

A silicon oxide film is preferred as the oxide film 3. Specifically, aSiO₂ film, an oxide film having TEOS as a raw material, or a similarfilm can be used.

A preferred thickness of the oxide film 3 is from 2,000 Å to 8,000 Å,and a thickness of about 5,000 Å is even more preferred.

The silicon nitride film 4 is provided as a protection film. The siliconnitride film 4 which has excellent water resistance is a favorableprotection film.

The silicon nitride film 4 is preferred to be high in nitrogen contentin order to supply nitrogen atoms efficiently to the titanium nitridefilm 7 which is arranged so as to be in contact with the silicon nitridefilm 4. Specifically, preferred nitrogen content in the silicon nitridefilm is 1.2 times higher than the silicon content or more in atomiccomposition ratio. The nitrogen content in the silicon nitride film 4can be measured by, for example, X-ray photoelectron spectroscopy (XPS).

A preferred thickness of the silicon nitride film 4 is from 5,000 Å to15,000 Å, and a thickness of about 10,000 Å is even more preferred.

In the semiconductor device 10 of FIG. 1, the oxide film 3 is formedbetween the silicon nitride film 4 and the titanium nitride film 7 in aregion outside the third opening portion 93 which lessens a differencein stress between the silicon nitride film 4 and the titanium nitridefilm 7 compared to the stress difference in a region inside the thirdopening portion 93 in which a part of the silicon nitride film 4 that isplaced in this region is in contact with the titanium nitride film 7.

In the semiconductor device 10 of FIG. 1, the pad portion 8 which ismade of aluminum or an aluminum alloy and the silicon nitride film 4 arenot in contact with each other. This prevents a crack caused by a stressdifference between the pad portion 8 and the silicon nitride film 4. Incontrast, when the pad portion 8 and the silicon nitride film 4 are incontact with each other, for example, a large stress difference betweenthe pad portion 8 and the silicon nitride film 4 can cause a crack inthe silicon nitride film 4, which has the possibility of affecting thereliability of the semiconductor device 10.

The wiring 6 is made of aluminum or an aluminum alloy. Examples of thealuminum alloy used include an alloy of aluminum, silicon, and copper,an alloy of aluminum and copper, and an alloy of aluminum and silicon.

A preferred thickness of the wiring 6 is from 3,000 Å to 30,000 Å, and athickness of about 20,000 Å is even more preferred.

The titanium nitride film 7 is an anti-reflection film and also servesas a wiring.

A preferred thickness of the titanium nitride film 7 is from 250 Å to800 Å, and a thickness of about 400 Å is even more preferred.

In FIG. 1 and FIG. 2, a side surface of the wiring 6 placed around thepad portion 8 is indicated by a symbol 6 a. A side surface of thetitanium nitride film 7 placed around the pad portion 8 is indicated bya symbol 7 a.

The pad portion 8 illustrated in FIG. 2 has a substantially square shapein plan view.

The wiring 6 in which the pad portion 8 is formed has a width d2 asillustrated in FIG. 2, and a width of 100 μm or more is preferred as thewidth d2.

The distance from the side surface 6 a of the wiring 6 which forms thepad portion 8 and the perimeter of the pad portion 8 to the inner wallof the third opening portion 93 is d3 in plan view as illustrated inFIG. 2, and a distance of from 1.0 μm to 9.2 μm is preferred as thedistance d3.

The shortest distance in plan view between the inner wall of the thirdopening portion 93 and an outer edge of the pad portion 8 (the outeredge is where the first opening portion 91 and the second openingportion 92 overlap with each other in plan view), in other words, thewidth of a part of the titanium nitride film 71 that is placed insidethe third opening 93 in plan view, is d1 as illustrated in FIG. 2, and adistance of from 0.8 μm to 9.0 μm is preferred as the shortest distanced1. A distance of from 0.8 μm to 1.2 μm is even more preferred as theshortest distance d1. When the distance d1 between the inner wall of thethird opening portion 93 and the outer edge of the pad portion 8 in planview is 0.8 μm or longer, the effect of preventing the corrosion of thetitanium nitride film 7 with the absence of the oxide film 3 inside thethird opening portion 93 in plan view is remarkable. It is preferredthat the distance d1 between the inner wall of the third opening portion93 and the outer edge of the pad portion 8 in plan view is 9.0 μm orshorter so that the downsizing of the semiconductor device is hardlyaffected by providing a region that does not contain the oxide film 3inside the third opening portion 93 in plan view.

[Method of Manufacturing Semiconductor Device]

A method of manufacturing a semiconductor device according to thepresent invention is described next by taking as an example a method ofmanufacturing the semiconductor device of FIG. 1 and FIG. 2. FIG. 3 toFIG. 8 are process views for illustrating an example of the method ofmanufacturing the semiconductor device of FIG. 1 and FIG. 2. FIG. 7 is aplan view for illustrating planar arrangement around the pad portion inthe step of FIG. 6. The horizontal direction in FIG. 7 corresponds tothe horizontal direction in FIG. 6.

To manufacture the semiconductor device 10 illustrated in FIG. 1 andFIG. 2, the interlayer insulating film 2 is formed first on one of theprincipal surfaces of the substrate 1, and a wiring layer 5 whichincludes the wiring 6 and the titanium nitride film 7 is formed on theinterlayer insulating film 2.

Specifically, the interlayer insulating film 2 is formed on thesubstrate 1 as illustrated in FIG. 3 by chemical vapor deposition (CVD)or other methods. The wiring 6 is then formed on the interlayerinsulating film 2 by sputtering or other methods (a wiring step).

The titanium nitride film 7 is formed next on the wiring 6 asillustrated in FIG. 3 by reactive sputtering that uses argon gas (Ar)and nitrogen gas (N₂) (an anti-reflection film forming step).

Next, the wiring 6 and the titanium nitride film 7 are patterned into agiven shape as illustrated in FIG. 4 with the use of a knownphotolithography method and a known etching method. In the exampleillustrated in FIG. 1 and FIG. 2, the wiring layer 5 which includes thewiring 6 and the titanium nitride film 7 is formed by patterning thewiring 6 and the titanium nitride film 7 both into the same shape.

The oxide film 3 is formed next on the wiring layer 5 which includes thewiring 6 and the titanium nitride film 7 so as to cover the wiring layer5 as illustrated in FIG. 5 by plasma CVD or other methods.

The oxide film 3 is patterned next as illustrated in FIG. 6 with the useof a known photolithography method and a known etching method. The thirdopening portion 93 which pierces the oxide film 3 and exposes thetitanium nitride film 7 at the bottom as illustrated in FIG. 6 and FIG.7 is formed in this manner (a third opening portion forming step). InFIG. 6 and FIG. 7, a side surface of the patterned wiring 6 is indicatedby the symbol 6 a, and a side surface of the patterned titanium nitridefilm 7 is indicated by the symbol 7 a.

Etching gas used to etch the oxide film 3 can be, for example, a mixedgas containing CHF₃, CF₄, and Ar.

Next, the silicon nitride film 4 is formed on the oxide film 3 and abovethe third opening portion 93 as illustrated in FIG. 8 by plasma CVD orother methods (a protection film forming step).

It is preferred to give the silicon nitride film 4 a high nitrogencontent by forming the silicon nitride film 4 under a condition in whichthe flow rate of gas containing nitrogen (N₂ or NH₃) is set high inplasma CVD, in order to supply nitrogen atoms efficiently to thetitanium nitride film 7 which is arranged so as to be in contact withthe silicon nitride film 4.

Next, a known photolithography method and a known etching method areused to etch the silicon nitride film 4 and the titanium nitride film 7successively with the use of the same mask and the same etching gas. Inthis manner, the pad portion 8 which exposes the wiring 6 at the bottomthrough the silicon nitride film 4 and the titanium nitride film 7 isformed inside the third opening portion 93 in plan view as illustratedin FIG. 1 (a pad portion forming step).

Etching gas used to etch the silicon nitride film 4 and the titaniumnitride film 7 can be CF₄ gas, for example.

In this embodiment, it is preferred to form the pad portion 8 in the padportion forming step at a place where the shortest distance d1 in planview between the inner wall of the third opening portion 93 and theouter edge of the pad portion 8 (the outer edge is where the firstopening portion 91 formed in the silicon nitride film 4 and the secondopening portion 92 formed in the titanium nitride film 7 overlap witheach other in plan view) (in other words, the width of the part of thetitanium nitride film 71 that is placed inside the third opening portion93 in plan view) is from 0.8 μm to 9.0 μm. With the distance d1 set tofrom 0.8 μm to 9.0 μm, the resultant semiconductor device 10 is hardlyaffected in terms of downsizing and effectively prevents the corrosionof the titanium nitride film 7.

Through the steps described above, the semiconductor device 10illustrated in FIG. 1 is obtained.

In the semiconductor device 10 according to this embodiment, the padportion 8 is formed at a place where the first opening portion 91 formedin the silicon nitride film 4 and the second opening portion 92 formedin the titanium nitride film 7 overlap with each other in plan view, andis inside the third opening portion 93 formed in the oxide film 3 inplan view, and the silicon nitride film 4 is formed on top of and incontact with the titanium nitride film 7 inside the third openingportion 93 in plan view. This makes the titanium nitride film 7 servingas an anti-reflection film resistant to corrosion, thereby giving highreliability to the semiconductor device 10.

In addition, in the semiconductor device 10 according to thisembodiment, the pad portion 8 is formed at a place where the firstopening portion 91 formed in the silicon nitride film 4 and the secondopening portion 92 formed in the titanium nitride film 7 overlap witheach other in plan view, and is inside the third opening portion 93formed in the oxide film 3 in plan view. The pad portion 8 made ofaluminum or an aluminum alloy is therefore not in contact with thesilicon nitride film 4. There is accordingly no chance for a drop inreliability of the semiconductor device 10 that is caused by a stressdifference between the pad portion and the silicon nitride film as whenthe pad portion made of aluminum or an aluminum alloy and the siliconnitride film are in contact with each other.

In the method of manufacturing the semiconductor device 10 according tothis embodiment, the pad portion 8 exposing the wiring 6 at the bottomis formed by etching the silicon nitride film 4 and the titanium nitridefilm 7 successively with the use of the same mask and the same etchinggas, and efficient production of the semiconductor device 10 isconsequently accomplished.

In contrast, with the technology described in Japanese Patent No.5443827, the anti-reflection film made of titanium nitride is removed byetching after the first surface protection film formed from a siliconoxide film is patterned by etching in order to form the first openingportion. It is difficult to etch a silicon oxide film and a titaniumnitride film with the use of the same etching gas. The trouble ofswitching the etching gas at the time when the titanium nitride film isetched therefore cannot be eliminated even by, for example, using thesame mask to etch the silicon oxide film and the titanium nitride film,and an obstacle to the improvement of productivity of the semiconductordevice 10 remains.

The semiconductor device according to the present invention is notlimited to the semiconductor device 10 of the embodiment describedabove.

The description given above on the embodiment takes as an example a casein which the pad portion 8 in the semiconductor device 10 has asubstantially square shape in plan view. However, the shape of the padportion 8 in plan view is not particularly limited. The shape of the padportion 8 in plan view may be a quadrangular shape, for example, asubstantially rectangular shape, a substantially rhomboidal shape, or asubstantially trapezoidal shape, or may be a substantially circularshape, or may be a polygonal shape, for example, a substantiallytriangular shape, a substantially pentagonal shape, or a substantiallyhexagonal shape.

The description given above on the embodiment takes as an example a casein which the semiconductor device 10 has one wiring layer 5 includingthe wiring 6 and the titanium nitride film 7. In addition to the wiringlayer described above, one or more wiring layers made of known materialsmay be included. When the semiconductor device 10 is provided with aplurality of wiring layers, it is preferred for the wiring layer 5 thatincludes the wiring 6 and the titanium nitride film 7 to be the topmostwiring layer.

The semiconductor device according to the present invention may furtherinclude layers having various functions to suit its use.

[Comparison]

Now, effects of the present invention are further clarified from thedescription of example for comparison according to the presentinvention. The present invention is not limited to the followingexamples, and modifications can be made thereto as appropriate withinthe range not changing the gist of the present invention.

Example 1

A semiconductor device of Example 1 illustrated in FIG. 1 was obtainedby a manufacturing method described below.

First, the interlayer insulating film 2 was formed from a SiO₂ film onthe substrate 1 made of silicon as illustrated in FIG. 3 by CVD. Thewiring 6 made of aluminum and having a thickness of 20,000 Å was thenformed on the interlayer insulating film 2 by sputtering (the wiringstep).

The titanium nitride film 7 having a thickness of 400 Å was formed nexton the wiring 6 by reactive sputtering that used argon gas (Ar) andnitrogen gas (N₂) (the anti-reflection film forming step).

Next, the wiring 6 and the titanium nitride film 7 were patterned asillustrated in FIG. 4 with the use of photolithography and etching toform the wiring layer 5 including the wiring 6 and the titanium nitridefilm 7.

The oxide film 3 having a thickness of 5,000 Å was formed next from aSiO₂ film on the wiring layer 5 including the wiring 6 and the titaniumnitride film 7 as illustrated in FIG. 5 by plasma CVD so as to cover thewiring layer 5.

The oxide film 3 was then patterned with the use of photolithography andetching to form the third opening portion 93 which pierced the oxidefilm 3 and exposed the titanium nitride film 7 at the bottom asillustrated in FIG. 6 and FIG. 7 (the third opening portion formingstep).

A mixed gas containing CHF₃, CF₄, and Ar was used as etching gas to etchthe oxide film 3.

Next, the silicon nitride film 4 having a thickness of 10,000 Å wasformed on the oxide film 3 and above the third opening portion 93 asillustrated in FIG. 8 by plasma CVD (the protection film forming step).

The silicon nitride film 4 was given a high nitrogen content by formingthe silicon nitride film 4 under a condition in which the flow rate ofgas containing nitrogen (N₂ or NH₃) is set high in plasma CVD.

Next, the silicon nitride film 4 and the titanium nitride film 7 wereetched successively with the use of the same mask and the same etchinggas by photolithography and etching to form the pad portion 8 whichexposed the wiring 6 at the bottom through the silicon nitride film 4and the titanium nitride film 7, inside the third opening portion 93 inplan view as illustrated in FIG. 1 (the pad portion forming step).

Etching gas used to etch the silicon nitride film 4 and the titaniumnitride film 7 was CF₄ gas.

Through the steps described above, the semiconductor device 10 ofExample 1 illustrated in FIG. 1 was obtained.

The distance d1 in plan view between the inner wall of the third openingportion 93 and the outer edge of the pad portion 8 in the obtainedsemiconductor device 10 of Example 1 was 1.0 μm. The width d2 of thewiring 6 in which the pad portion 8 was formed was 100 μm or more. Thedistance d3 in plan view from the inner wall of the third openingportion 93 to the side surface 6 a of the wiring 6 which formed the padportion 8 and the perimeter of the pad portion 8, was 9.0 μm.

Comparative Example 1

A semiconductor device 11 of Comparative Example 1 illustrated in FIG. 9was obtained in the same manner as in Example 1, except that the siliconnitride film 4 was formed on the oxide film 3 without performing thethird opening portion forming step, and that the pad portion 8 exposinga wiring at the bottom through the silicon nitride film 4, the oxidefilm 3, and the titanium nitride film 7 was formed with the use ofphotolithography and etching. Members of the semiconductor device 11illustrated in FIG. 9 that are the same as those of the semiconductordevice 10 illustrated in FIG. 1 are denoted by the same symbols, anddescriptions on the members are omitted.

In steps of manufacturing the semiconductor device 11 of ComparativeExample 1, CF₄ gas was used as etching gas to etch the silicon nitridefilm 4. The etching gas was then switched to a mixed gas containingCHF₃, CF₄, and Ar to etch the oxide film 3. Thereafter, the etching gaswas switched to CF₄ gas to etch the titanium nitride film 7.

The pad portion 8 in the semiconductor device 11 of Comparative Example1 is formed at a place where the first opening portion 91 formed in thesilicon nitride film 4, the third opening portion 93 formed in the oxidefilm 3, and the second opening portion 92 formed in the titanium nitridefilm 7 overlap with one another in plan view.

The thus obtained semiconductor devices 10 and 11 of Example 1 andComparative Example 1 were subjected to the following long-termreliability test (THB) involving bias application under ahigh-temperature and high-humidity environment, and were evaluated bycriteria given below.

“Long-Term Reliability Test (THB)”

The semiconductor device 10 of Example 1 and the semiconductor device 11of Comparative Example 1 were each packaged into a resin package tocreate twenty-two samples for each semiconductor device. A voltage wasapplied to each sample for 1,000 hours in an environment in which thetemperature was 85° C. and the humidity was 85%. Each resin package wasthen opened, and a portion around the pad portion was observed with amicroscope to conduct an appearance test by the following criteria.

“Criteria”

Appearance is fine: there is no corrosion, detachment, or discolorationin the pad portion or around the pad portion.

Appearance is defective: corrosion, detachment, or discoloration isfound in the pad portion or around the pad portion.

After the long-term reliability test (THB), the number of defectiveappearance samples (the number of defective appearance samples/the totalnumber of samples) was 0/22 in the semiconductor device of Example 1,and 3/22 in the semiconductor device of Comparative Example 1.

It is clear from this result that corrosion of the titanium nitride filmwas prevented better in the semiconductor device 10 of Example 1 than inthe semiconductor device 11 of Comparative Example 1.

What is claimed is:
 1. A semiconductor device, comprising: a substrate;a wiring formed above the substrate; a titanium nitride film formed onthe wiring; an oxide film formed on the titanium nitride film; a siliconnitride film formed on the oxide film; and a pad portion exposing thewiring, and formed within a region where a first opening portion formedin the silicon nitride film and a second opening portion formed in thetitanium nitride film overlap with each other in a plan view, and beinginside a third opening portion formed in the oxide film in the planview, the silicon nitride film being formed on top of and in partialcontact with the titanium nitride film inside the third opening portionin the plan view.
 2. The semiconductor device according to claim 1,wherein a shortest lateral distance between the overlap of the firstopening portion and the second opening portion in the plan view and aninner wall of the third opening portion is from 0.8 μm to 9.0 μm.